The present invention relates to novel porous amorphous metallo phosphate materials. More particularly the present invention relates to materials comprising metal oxides and phosphorus oxide present as phosphate having very large surface areas and very narrow pore distributions. The compounds are stable solid materials finding use as molecular sieves, catalysts and as catalyst supports.
It has been previously known to prepare metallo phosphate compositions. Early work involved the mixing and calcining the solid mixtures of oxides or the acid treatment of metal oxides or mixtures thereof.
In U.S. Pat. No. 2,282,602, metallic oxides such as the oxides of copper, magnesium, iron, zinc, aluminum, tin and nickel were combined with phosphorus pentoxide and the solid mixture calcined at a temperature of about 600.degree. C.-800.degree. C. A chemical reaction was believed to occur in the mixture. In U.S. Pat. No. 2,330,115, bauxite was treated with a strong mineral acid such as phosphoric acid to produce an isomerization catalyst. Similary, in U.S. Pat. No. 3,969,273 alumina and a phosphate compound such as phosphoric acid or ammonium phosphate were combined and calcined to yield a catalyst support for hydrocarbon conversion processes.
Alumino phosphate compositions having relatively large pore sizes have also been prepared by formation of gels or by coprecipitation followed by calcination. In U.S. Pat. No. 3,342,750, and alumninum phosphate gel was prepared by contacting aluminum chloride, phosphoric acid and ethylene oxide in an aqueous solution. The gel was then extracted with a low boiling alcohol to remove ethylene chlorohydrin and the resulting product calcined. Pore sizes were found to range from about 30 Angstrom units (A) to about 100 A. Later workers reported that substitution of 10 percent ammonia solution for ethylene oxide neutralizer resulted in aluminum phosphates of reduced surface area.
In U.S. Pat. No. 3,427,257, a catalyst system comprising vanadium oxide and an organic phosphorous oxy compound was described. The catalyst was employed in combination with an alkyl aluminum cocatalyst for the polymerization of ethylene.
U.S. Pat. No. 3,879,310, described the preparation of surface stabilized active alumina by incorporating small amounts of phosphate ion in pseudoboehmitic alumina. The stabilizer could be prepared by adding ammonium phosphate salts to a slurry of precipitated alumina. Upon heating during a thermal activation step, the phosphate salts decomposed to release volatile ammonia.
In U.S. Pat. No. 3,904,550, an alumina-aluminum phosphate material for use as a catalyst support was prepared by the reaction of an aluminum alkoxide with an aqueous solution containing phosphate ions. Suitable aqueous solutions included those of phosphoric or pyrophosphoric acid. After reaction to form a precipitate and impregnation with a catalytic metal, the materials were calcined.
In U.S. Pat. No. 4,066,572, inorganic aluminum salts and water-soluble phosphorus salts were co-precipitated by adjusting the solution pH to form an amorphous phosphate-alumina gel which upon calcination yielded catalysts and catalyst supports. The products were characterized by fairly large average pore diameters greater than 100 A. Less than 30 percent of the total pore volume consisted of pores less than 100 A.
In U.S. Pat. No. 4,080,311, thermally stable alumina-aluminum phosphate composite precipitates were prepared by forming an aqueous solution of aluminum cations and phosphate ions having phosphate/aluminum ratios within the narrow range of from 0.82:1 to 0.25:1. The solutions were subsequently neutralized with ammonia gas or a basic ammonium compound and the resulting precipitate calcined. The composite precipitate so formed had a surface area of from about 100 m.sup.2 /g to about 200 m.sup.2 /g and an average pore size from about 75 A to 150 A.
In U.S. Pat. No. 4,233,184, high surface area, amorphous, phosphate-alumina compositions were prepared by reacting aluminum alkoxides with organic phosphates in the presence of moist air. Upon calcination, relatively high surface area compositions having aluminum phosphate content from 10 to about 90 weight percent were prepared.
Efforts to provide high surface area aluminum phosphate materials with narrow distribution of pore sizes less than 100 A and particularly less than about 50 A have not been achieved by standard techniques of coprecipitation, extraction and calcination. Recently, however, E. M. Flanigen et al. reported the preparation of novel crystalline microporous alumino phosphate compositions by hydrothermal crystallization of alumino phosphate gels containing a molecular structure forming template. The compositions were found to possess uniform pores with dimensions from about 3 A to 10 A. The work is described in U.S. Pat. No. 4,310,440.
In U.S. Pat. No. 4,360,474, certain metal-containing derivatives of polyphosphoric acid partial esters were described. The materials were found to possess useful corrosion-inhibiting properties. As used herein, such materials prior to drying are referred to as metallo-organo phosphate gels.